10-BMP-De-watering Activities.pdf

DE-WATERING AND NON-STORMWATER DISCHARGES

MAINTENANCE BEST MANAGEMENT PRACTICE (BMP) 2.5

FACTSHEET U.S. ARMY GARRISON

PICATINNY, NEW JERSEY

PURPOSE: The purpose of this factsheet is to provide guidance on stormwater pollution prevention practices necessary during permitted de-watering activities that result in non-stormwater discharges to comply with The Picatinny General Permit and the Stormwater Polluton Prevention Plan.

Stormwater pollution prevention (SWPP) practices include implementing best management practices (BMPs) when performing de-watering activities that result in non-stormwater discharges. It is important to follow SWPPP practices when discharging non-stormwater so that constituents from the water and de-watering activities do not cause unnecessary and unlawful discharging of harmful pollutants into the Picatinny waterways. If best management practices are not followed, harmful pollutants can migrate into groundwater, wetlands and waterways (creeks, rivers, streams).

APPROACH: When illicit discharge complaint investigations or routine stormwater program audits indicate that impacts to water resources are occurring due to poor housekeeping and best management practices, the Directorate of Public Works, Environmental and Natural Resources Division is responsible for reviewing daily operations and procedures to identify potential pollutants and provide Best Management Practices (BMPs) and good housekeeping measures that will reduce or eliminate the pollutant.

POLLUTION PREVENTION: Pollution prevention starts with good housekeeping measures and implementation of proper BMPs. In order to comply with MS4 and ISW permit conditions, it is very important that excess chemicals in waste water from non-stormwater sources do not get discharged into storm drains and leach into groundwater. The pollutants found in non-stormwater sources (such as chlorine, grease, cleaning solutions, heavy metals and suspended solids) pose a threat to natural water ways and can be detrimental to fish and other aquatic organisms. The discharge of these harmful pollutants into storm drains and ground water can be reduced if proper BMPs and good housekeeping measures are implemented.

LEGAL AUTHORITY - ILLICIT/NONSTORMWATER

DISCHARGES: The Picatinny General Permit and Stormwater Pollution Prevention Plan prohibit illicit discharge. An illicit discharge is any discharge to the storm sewer system that is not composed entirely of stormwater. While illicit discharges are strictly prohibited, there are some circumstances in which non-stormwater discharges are permitted but require mandatory Best Management Practices (BMPs) to be implemented prior to discharge. These activities include:

• De-watering of potable water which includes;

o Drinking water tank draw downs o Waterline flushing o Fire hydrant flushing o Water main/pipeline flushing

• Swimming pool or hot tub draining (excludes salt water pools, salt water pools should never be drained into a storm water system)

BEST MANAGEMENT PRACTICES- DE-

WATERING OF POTABLE WATER

The water contained in drinking water tanks and waterlines is potable-clean water. Small amounts of chlorine are added to potable water to make it safe for human use. Chlorine is a highly efficient disinfectant, and is added to public water supplies to kill disease-causing pathogens, such as bacteria, viruses, and protozoans, that commonly grow in water supply reservoirs, on the walls of water mains and in storage tanks. Although very low levels of chlorine in potable water is safe for humans, it can be detrimental to natural systems if released into the environment.

Chlorine, even in the low amounts found in tap water, will give marine invertebrates and fish chemical burns. In fish, chlorine is absorbed into the bloodstream and causes burns throughout the fish. It has a

Similar effect on invertebrates, who absorb it through their surfaces. These burns can cause serious damage to marine organisms. The following BMPs must be followed in order to properly and lawfully discharge potable water into storm drains.

De-chlorination of Potable water: All potable water must be properly de-chlorinated prior to discharge. In most cases this can be done by simply allowing enough time for chlorine to dissipate. This is usually achieved by allowing water to stand for 7-14 days. Chlorine testing kits are readily available and easy to use. Prior to draining make sure there is no detectable chlorine (less than .01mg/l is acceptable). In the event that time does not allow for this method of de-chlorination, it can also be done quickly and easily by using the following methods:

1. De-chlorination mats/strips and tablets – De-chlorination mats consisted of a mesh type material with pockets to hold de-chlorination tablets. These mats are simple laid perpendicularly across the flow path of water before it enters storm system. It is important to make sure all water from the source is crossing mat. Check chlorine residual from downstream sample to ensure adequate de-chlorination is taking place. This method of De-chlorination is often used during tank draining and pipeline flushing.

2. De-chlorination diffuser- De-chlorination diffusers are devices that are designed to either reattach to a fire hydrant or fire hose. These devices have either a chamber for de- chlorination tablets or they are allow for de- chlorination mats to attach to the face. The device is simply attached to hydrant or hose and water filters through it.

This method of de-chlorination is often used during hydrant testing/flushing and pipeline flushing/de- watering. If flow rates are high, volume is high or discharge uncharacteristically high chlorine levels than additional BMP’s may be needed.

BEST MANAGEMENT PRACTICES – DRAINING

SWIMMING POOLS AND HOT TUBS

Just like our drinking water, swimming pools and hot tubs must be made safe for use. The most common chemicals added to swimming pools and hot tubs are chlorine and salt. Just like in drinking water these chemicals are used because they are powerful disinfectants but if they get released into the environment, it could have detrimental effects on the natural systems. The following BMPs must be followed in order to properly and lawfully discharge swimming pool and hot tub water into storm drains and sewer systems.

Chlorinated Hot Tubs and Pools: Ideally swimming pools and hot tubs should be discharged into sanitary sewer systems. This is because swimming pools and hot tubs often contain larger amounts of chlorine and other chemicals then potable water. Sending pool/hot tub water to a treatment facility via sanitary sewer lines will ensure most of the chemicals get filtered out. If draining water to sanitary sewer isn’t feasible than proper de-chlorination procedures must be implemented.

In most cases this can be done by simply allowing enough time for chlorine to dissipate by allowing water to stand for at least two weeks (14 days). Chlorine testing kits are readily available and easy to use. Prior to draining make sure there is no detectable chlorine (less than .01mg/l is acceptable). In the event that time does not allow for this method of de- chlorination, the same methods of de-chlorinating of potable water can be applied to draining swimming pools and hot tubs but attentional de-chlorination supplies may have to be used to adequately de-chlorinate waste water.

EROSION AND SEDIMENT CONTROL WHILE DE-

WATERING

Evaluate Site Conditions: Prior to de-watering, it is very important to evaluate the site conditions. When releasing large amounts of water onto a landscape there is the potential to erode, suspend, and transport sediment into storm drains. Certain measures must be taken to minimize erosion and the transport of sediment to storm drains and receiving waters during the de-watering activities. It is especially important to evaluate your flow path if you are discharging large volumes of water or anticipate high flow rates.

Denuded/Exposed Soil Areas – Denuded and exposed areas are especially susceptible to erosion. If possible, flow should be diverted away from susceptible areas to areas that are well vegetated and stable. If avoiding these areas is not feasible then additional erosion and sediment controls will need to be implemented.

Flow Path – If possible, remove all loose soil and debris from flow path. Use a broom to sweep up gutters and curbs of loose materials like dirt, dust, and other debris that can be picked up and moved into the storm drains. To prevent flooding, make sure the storm drains in which you will be discharging to, are unclogged and clear of debris. If you discover a problem with a storm drain call DPW.